1. Field of the Invention
The present invention relates to latch tools that are utilized in a subsea environment. More particularly, the present invention the relates to latch tools that can be remotely engaged and disengaged. Additionally, the present invention relates to latch tools that can be utilized in association with a subsea test tree.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
During well testing (drilling) operations and the like, which are carried out from a floating vessel, such as a drillship or semi-submersible, well control is achieved by a subsea blowout preventer, which is mounted on the sea-bed to the wellhead. Such blowout preventers typically comprise a tubular central housing on which are mounted a number of sets of hydraulic rams. The rams are axially spaced along the housing. The lower rams, or pipe rams, are provided with semi-circular sealing faces, so that when these rams are activated the semi-circular faces mate with the outer surfaces of the well tool. The uppermost set of rams are known as shear rams and are provided with cutting surfaces which can cut through or close the bore of the well tool and isolate the pressurized reservoir fluid from the riser and the upper part of the well tool.
In oil and gas well testing, well pressure control equipment is utilized in addition to the downhole test equipment mounted at the end of the test string, the well pressure control equipment being located above the wellhead and blowout preventer on the landing string. This equipment provides various safety features and allows for complete well control.
One of the tools utilized in well testing is a subsea test tree, a safety valve which is located inside the blowout preventer. During well test operations, it is necessary to control both the tubing and annulus pressures, that is the pressure within the string and the pressure between the string and the riser, well casing and well lining. The subsea safety tree provides a primary safety system to control tubing pressure and provide means to disconnect the riser rapidly and safely from the well should adverse conditions occur, such as bad weather or loss of the positioning system of the floating vessel. This is partly achieved by providing failsafe valves in the tree, which, for example, are held open during normal operating conditions by supplied hydraulic pressure. If the hydraulic pressure is cut off, the valves will close, isolating the test string below the tree. A upper portion of the tree may be unlatched from the lower portion of the tree containing the valves, and the landing string and other well pressure control equipment located above the tree withdrawn.
In order to achieve these proper connections between the various components, latching tools are utilized. Such latching tools can take on a wide variety of configurations. It is important to the operation of any latching tool that a complete and structurally sound seal is established between the various components. Additionally, it is necessary for the latching tool to be properly hydraulically operated so that the latching tool can be easily connected and disconnected from the various components. It is very difficult to achieve the structurally sound connection while also allowing the easy connection and disconnection of the latch tool to the components. Additionally, and furthermore, the latch tool should have a secondary mechanism whereby the release of the latch tool from the component can be achieved by alternate techniques. As such, such an arrangement would avoid the necessity of deploying subsea operations in order to properly release the latch tool from the components.
In the past, various patents have issued relating to latching systems associated with subsea components, such as a test tree. For example, U.S. Pat. No. 4,116,272, issued on Sep. 26, 1978 to B. Q. Barrington, describes a hydraulically-operated subsea test tree for placement in a blowout preventer stack. A quick-release is disclosed which operates to release a stinger from a conduit leading to the surface when pressure is applied to one side of a second set of closed rams above the pressure which exists in the annulus exterior of the quick release mechanism.
U.S. Pat. No. 4,320,804, issued on Mar. 23, 1982 to R. T. Brooks, describes a latching system for use with subsea test tree. This system includes a first rocker section carryable with an upper conduit portion. A second rocker section is carryable with a second conduit portion. A lock means has a recess contoured for securement over the rocker sections and is manipulatable over the first and second rocker sections to locked and unlocked positions. Shiftable means are carried across the lock means to a first position whereby the lock means are engaged over the rocker sections and the conduit portions are secured together. A shiftable means is moved to a second position whereby the lock means are disengaged from the second rocker section and the conduit portions are in disengaged position. A second lock means is also are provided for additional securement.
U.S. Pat. No. 4,375,239, issued on Mar. 1, 1983 to Barrington et al., describes an acoustic subsea test tree and method. A hydraulically-powered latch connects and disconnects the upper and lower portions of the subsea test tree in response to acoustic command signals.
U.S. Pat. No. 4,436,157, issued on Mar. 13, 1984 to R. T. Brooks, shows a latch mechanism for subsea test tree. The test assembly provides inner and outer latching connections between upper and lower portions of a tubular conduit extending to a production zone within the well. The test assembly has a valve means in the lower conduit portion manipulatable between open and closed positions by a reciprocable actuator to control flow of fluid within the conduit. A retaining means is provided for each of the inner and outer latches to ensure that such latches may not be disengaged when the valve means is in other than an open position. The retaining means are operable by either the application of fluid pressure or through mechanical manipulation of the tubing string to be shifted to a non-retaining position relative to both the inner and outer latches. This permits selective disconnection and reconnection of the upper and lower portions of the tubular conduit.
U.S. Pat. No. 6,026,905, issued on Feb. 22, 2000 to V. Garcia-Soule, describes a subsea test tree that includes a latch head assembly, a valve assembly, and a ramlock assembly interconnected between the latch head assembly and the valve assembly. The latch head assembly may be actuated to decouple an upper portion of the tubular string from a lower portion of the tubular string. In the event of an emergency, the pipe rams may be closed on the ram lock assembly, the valves in the valve assembly may be closed, and the upper portion of the tubular string may be retrieved, or otherwise displaced away from the lower portion.
U.S. Pat. No. 8,336,630, issued on Dec. 25, 2012 to J. A. Kerr, discloses a subsea completion testing tree for connection to a tubular string which includes a lower tree portion having a control valve, an upper tree portion separably connected to the lower tree portion at a latch, a circulation valve connected with the upper tree portion, and a retainer valve connected with the upper tree portion between the circulation valve and the latch.
It is an object of the present invention to provide a subsea latch tool that can easily be engaged and disengaged from the subsea components.
It is another object of the present invention to provide a subsea latch tool that can be used in association with a subsea test tree.
It is another object of the present invention to provide a subsea latch tool which can provide a secondary or back-up mechanism for the disengagement of the subsea latch tool.
It is still another object of the present invention to provide a subsea latch tool which can be engaged and disengaged for a large number of cycles.
It is still another object of the present invention to provide a subsea latch tool which can be remotely controlled through the use of hydraulic pressure.
It is still a further object of the present invention to provide a subsea latch tool which avoids plastic deformation of the locking component.
It is still a further object of the present invention to provide a subsea latch tool which is easy to use, easy to manufacture and relatively inexpensive.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.